1. Related Application
This application claims the benefit of U.S. Provisional Application Ser. No. 60/035,354, filed on Feb. 26, 1997, for Apparatus for Securing Induction Coils Within an Induction Coil Module.
2. Field of the Invention
The present invention is related to methods and apparatus for suspending induction coils within induction coil modules in an induction furnace. More particularly, the present invention is related to methods and apparatus including flexible connectors used to suspend induction coils and connect them to a support bar within the induction coil module.
3. Technical Background
Steel has been part of some of the greatest achievements in history: it was the "iron horse" and rails that helped create a nation out of frontiers; it is the backbone of bridges, the skeleton of skyscrapers, the framework of our automobiles and appliances. It is the high-strength, better-than-plastic frames for eyeglasses; it is the stronger, more affordable, more-resilient-than-wood frame in new housing; it is the high-tech alloy used in the Space Shuttle's solid fuel rocket motor cases; and it is the coated, precision surgical instruments used in hospital operating rooms around the world. The production and processing of steel has become a core industry that in the last two decades has revolutionized its manufacturing processes, transformed its workforce, and collaborated with customers around the world to make stronger, lighter, more versatile steel at a lower cost to the consumer.
Consequently, new and emerging technologies for processing steel are being developed by those skilled in the art. For example, induction furnaces are being used to heat slabs, plates, or ingots of steel by introducing an electrical current that is caused to flow through the steel by means of electromagnetic induction. In operation, an induction furnace may receive a steel slab, plate, or ingot and thereby increase the average temperature of the slab, plate, or ingot up to and beyond melting point. After passing the slab, plate, or ingot through various environments of extreme heat as provided by several induction furnaces, the slab, plate, or ingot may be sent to a rolling mill for further processing.
As appreciated in the art, slabs, plates, or ingots of steel are generally moved along aisles of rollers and may be passed through one or more induction furnaces. The induction furnaces of the prior typically comprise a plurality of induction coils rigidly mounted to a housing frame of the furnace. Functionally, the induction coils provide a means for obtaining intermittent high voltage by way of high capacity electrical connectors and induce electrical currents into the steel slab, plate, or ingot to generate extremely high elevated temperatures. Because of the high density electromagnetic field created by the induction coils, there are considerable attraction and repulsion forces acting between each induction coil and the connection mechanisms attaching each induction coil to the furnace housing, thus resulting in substantial vibrations in the mechanical connectors of the induction furnace.
A significant disadvantage with induction furnaces of the prior art, however, is their tendency to experience comprehensive structural failure as a result of the vibrations caused by the cycling of electrical current through the induction coils during the heating process. Accordingly, the mechanical and structural connection mechanisms of prior art induction furnaces traditionally encounter severe stress fracturing and breakage. The investigation and study of failed connections has revealed that stress fractures have the potential of occurring everywhere there is a bolted or rigid connection, inclusive of the support rods and the fastener assembly securing the support rods to the induction coils. Because the connection mechanisms between the induction coils and the furnace housing are typically covered with massive layers of insulation and protective coatings, it is generally difficult to detect or even predict potential mechanical failures in the connections before they happen.
When an induction furnace fails, it generally results in significant down time of the furnace as well as the casting and/or roll lines. A maintenance team consisting of numerous engineers and skilled technicians is typically required to remove the induction furnace from the steel processing line and begin immediately rebuilding the unit. The down time for servicing and rebuilding an induction furnace module may be on the average a period of approximately two weeks. If the maintenance team works around the clock, an induction furnace may potentially be up and running within a week. Besides the time and energy involved in making the repairs to the mechanical connections of the induction furnaces, the cost for maintenance, repairs, and replacement parts can be a significant investment on the part of the steel mill, especially in view of the structural failures that are consistently encountered by prior art induction furnaces.
In an effort to reduce the structural fatigue and stress fracturing of the various mechanical connections of prior art induction furnaces, various remedies have been developed with little appreciable improvement. For example, heavier fasteners, different grades of steel support rods, and varying the electrical current and the on and off cycles of the coils have been undertaken. In addition, those skilled in the art incorporated a spring mounting mechanism in relation to the rigid structural rods attached to the furnace housing in an attempt to keep constant pull-back force on the rods.
While the foregoing prior art remedies have had little impact in reducing the number of induction coil failures, those skilled in the art developed induction furnace modules which replace the rigid structural rods with flexible mounting members that function to secure the support bar to the furnace housing. In structural design, the prior art flexible mounting member consists of a steel cable disposed between the furnace housing and the support bar having several induction coils rigidly attached thereto. The inclusion of flexible mounting members between the furnace housing and the support bar helps to alleviate some of the vibrational energy of the induction furnace, however, these prior art flexible mounting members have only seemingly delayed the imminent structural failure of the connection mechanisms of the induction furnace.
Thus, it would be an advancement in the art to provide improved methods and apparatus for attaching induction coils within induction coil modules. It would also be an advancement in the art to improve the overall attachment mechanisms used in induction furnaces.
Such methods and apparatus are disclosed and claimed herein.